Novel LISICON mixed conductors, Li4 ? 2xCoxGeO4

Abstract

A novel LISICON type ? solid solution range has been found in the system Li4 ? 2xCoxGeO4 for 0.15 ? x ? 0.8. The highest net conductivity, 8.4 ? 10?6Scm?1, was observed for x = 0.25 at 27 �C rising to 3.35 ? 10?3Scm?1 at 300 �C with an activation energy of 0.71 eV. A charge/discharge polarisation technique was used to investigate the transference number of these materials. Results corroborate those obtained by low frequency a.c. impedance measurements and show the occurrence of mixed Li+ ion and electronic conductivity. The relative amounts of each vary with composition; x = 0.25 has both the highest conductivity and the highest ionic transference number, 0.19.